CODEWITHSUNDEEP
javaiobufferedreader
overexchange
overexchange

Reputation: 1

character I/O stream vs Byte I/O stream in Java

Does Character stream concrete subclasses classes that inherit from abstract class Reader and abstract class Writer have their own implementations of I/O without relying on concrete subclasses of abstract class InputStream and abstract class OutputStream, which are byte based I/O?

I understand that character stream classes take care of character-encoding formats as additional responsibility, But,

Why do we have separate hierarchy given under abstract class Reader and abstract class Writer in addition to byte stream class hierarchy under abstract class InputStream and abstract class OutputStream?

Upvotes: 0

Views: 375

Answers (2)

Joop Eggen
Joop Eggen

Reputation: 109547

It was a huge language design decision at that time, that in java there is Unicode text, being able to combine all scripts:

  • Binary data: byte[], InputStream/OutputStream.
  • Text: String/char (16-bit UTF-16), Reader/Writer.

The step from binary data to text and inverse, always involves a conversion needing the encoding of the bytes.

As Java also uses wrapping child classes like BufferedReader, StringReader, base classes Reader/Writer where sensible. Java chose this, and:

In this way you can have a text processing method with a Reader parameter.

In contrast to C java thus has a separate byte type, and a 2-byte char type, holding UTF-16. In java one should almost never try to hold binary data in String, or cast byte to char.

Upvotes: 1

user207421
user207421

Reputation: 310884

Does Character stream concrete subclasses classes that inherit from abstract class Reader and abstract class Writer have their own implementations of I/O without relying on concrete subclasses of abstract class InputStream and abstract class OutputStream, which are byte based I/O?

No.

I understand that character stream classes take care of character-encoding formats as additional responsibility

Good.

But, why do we have separate hierarchy given under abstract class Reader and abstract class Writer in addition to byte stream class hierarchy under abstract class InputStream and abstract class OutputStream?

For the purpose you have just described. They are essentially a family of filters that redefine the I/O APIs in terms of chars rather than bytes.

Upvotes: 0

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